Lot of what you are asking is for you to determine if they are acceptable for you and your organization based on your usecases and SLAs. What acceptable for one may not acceptable for other. Let me briefly touch some topics here

- Pros and Cons of using Teiid

Data Virtualization, the space the Teiid is in solves many issues. There are books written on this topic why and what benefits DV provides. It provides transparency from sources, integration of disparate sources, creation canonical view models, creation enterprise data dictionary, easy creation of data services to name a few. On top of it, add any number Teiid specific features like data security

Lot of this depends upon the type of sources, latency and size of the data they are bringing to the JOIN to begin with. These are external to Teiid which it does not have any control on. Teiid has best query optimization engine in this space (even compared to commercial entities in this space). It is has excellent buffering technologies to handle millions of rows efficiently. Teiid does rule and cost based optimizations such that it generates optimal query to sources. These are some of credits Teiid earned from our customers over 13 years of development in this space. See Teiid history on the website.

There is reason Teiid is built on using JBoss AS. It is an Enterprise JEE Application Server used by thousands of corporations around the world. It provides best of technologies in things such as clustering, transactions, JCA etc which matter to Teiid most in providing such scalability. Teiid provides load balancing and failover either using software only or using external load balancers. You can deploy as many Teiid nodes as you wish in your cluster to meet your usecase needs.

- Teiid Support provided by community

What you not been getting answers from community?

No sane manager should approve to deploy their mission critical application solely based on community support. Community support is volunteering work, myself and any of other members do it when we have some time to spare and our willingness to help others in community and thus by promote Teiid project in general. You should NOT base support model based on the community support, if you need some SLAs. If this is your pet application running on your own machine that nobody care then that is fine.

This is where Red Hat fills the gap. Red Hat can provide you support and services based on your enterprise requirements that community falls short of. When you run into a production issue in the middle of night, nobody from community will come your rescue, but Red Hat support team will. Community does NOT release any patches on bugs you find, Red Hat does. Community is always moving ahead with new versions, Red Hat provides a stable version of Teiid to work with. These are just to name few advantages of buying support. Obviously that comes at a cost, if interested contact Red Hat Sales.